ch 5 nucleic acids excerpt -...
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BIOL221BIOL221
Ch5(excerpt)Ch5(excerpt)
NucleicAcidsNucleicAcids
NucleicAcidsNucleicAcids
• Storeandtransfergene3cinforma3on
• Gene
• Unitofinheritancethatcodesfortheaminoacidsequenceofapolypep3de
• Makesaprotein
• GenesaremadeofDNA
• Anucleicacid
TheRolesofNucleicAcidsTheRolesofNucleicAcids
• Twotypesofnucleicacids:
• Deoxyribonucleicacid(DNA)
• Ribonucleicacid(RNA)
• DNA
• Codesforproteins
• Providesdirec3onsforitsownreplica3on
• DirectssynthesisofmessengerRNA(mRNA)
• Containsinforma3onforproteinsynthesis
• Proteinsynthesisoccursinribosomes
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mRNA
Synthesis ofmRNA in thenucleus
DNA
NUCLEUSCYTOPLASM
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mRNA
Synthesis ofmRNA in thenucleus
DNA
NUCLEUS
mRNA
CYTOPLASM
Movement ofmRNA into cytoplasmvia nuclear pore
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mRNA
Synthesis ofmRNA in thenucleus
DNA
NUCLEUS
mRNA
CYTOPLASM
Movement ofmRNA into cytoplasmvia nuclear pore
Ribosome
AminoacidsPolypeptide
Synthesisof protein
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TheStructureofNucleicAcidsTheStructureofNucleicAcids
• PolynucleoFdes
• Nucleicacidpolymer
• NucleoFde
• Monomersofpolynucleo3de
• Consistsof
• Pentosesugar
• Phosphategroup
• Nitrogenousbase
• Adenine(A),Cytosine(C),Guanine(G),Thymine(T)
• Nucleoside
• por3onofanucleo3dewithoutthephosphategroup
5′ end
Nucleoside
Nitrogenousbase
Phosphategroup Sugar
(pentose)
(b) Nucleotide
(a) Polynucleotide, or nucleic acid
3′ end
3′C
3′C
5′C
5′C
Nitrogenous basesPyrimidines
Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)
Purines
Adenine (A) Guanine (G)
Sugars
Deoxyribose (in DNA) Ribose (in RNA)
(c) Nucleoside components: sugars
NucleoFdeMonomersNucleoFdeMonomers
• Twofamiliesofnitrogenousbases:
• Pyrimidines
• cytosine(C),thymine(T),anduracil(U)
• singlesix‐memberedring
• Purines
• adenine(A)andguanine(G)
• six‐memberedringfusedtoafive‐memberedring
• Deoxyribose
• SugarinDNA
• Ribose
• SugarinRNA
• Nucleo3de=nucleoside+phosphategroup
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NucleoFdePolymersNucleoFdePolymers
• Nucleo3dePolymers
• Linkedtogethertobuildapolynucleo3de
• Simplyunfinishednucleicacid
• Adjacentnucleo3des
• Joinedbyphosphodiesterbonds(covalent)
• Formbetweenthe–OHgrouponthe3′carbonofonenucleo3deandthephosphateonthe5′carbononthenext
• Createabackboneofsugar‐phosphateunits
• Withnitrogenousbasesasappendages
• ThesequenceofbasesalongaDNAormRNApolymerisuniqueforeachgene
TheDNADoubleHelixTheDNADoubleHelix
• Doublehelix
• Twopolynucleo3desspiralingaroundanimaginaryaxis,formingaDNAmolecule
• Nitrogenousbasesbondwithoneanotherinthemiddleincomplementaryfashion
• A‐T;C‐G
• Hydrogenbonds
• AnFparallel
• Twobackbonesruninopposite5′→3′direc3onsfromeachotherintheDNAdoublehelix
• OneDNAmoleculeincludesmanygenes
• Equalsonechromosome
DNAReplicaFonDNAReplicaFon
• Semi‐conservedmodel
• Oneparentstrandyieldstwodaughterstrands
• Eachdaughterstrandcontainshalfoforiginalparentstrand
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DNAandEvoluFonaryRelaFonshipsDNAandEvoluFonaryRelaFonships
• Sequencesofnucleo3desinDNA
• Passedfromparentstooffspring
• Twocloselyrelatedspecies
• AremoresimilarinDNA
• Thanaremoredistantlyrelatedspecies
• Determinedby%divergence